Conventional concrete trucks include large drum containers for mixing aggregate, sand and cement slurry together. The concrete is discharged from the drum into a hopper and down a chute to the desired discharge location, such as into a concrete pump or bucket.
After concrete has been fully discharged from the truck, the operator must rinse debris adhering to the discharge hopper and outlet chute before leaving the construction site. Accordingly, the contractor must provide a designated location at the construction site where this rinsing operation may occur. This is often inconvenient and inefficient, especially if the rinsing station is located at a site remote from the concrete discharge location.
Moreover, concrete truck wash-off can pose serious environmental concerns. In many cases precautions must be taken at the construction site to ensure that sediment and cementitious debris does not contaminate the site or adjoining waterways. Enforcement of environmental regulations at construction sites is becoming increasingly stringent and hence it is anticipated that this issue will become more prominent in the future.
Some concrete supply companies have developed truck-mounted wash-off containment systems in attempt to address this problem. However, existing systems are unreliable and are not user-friendly. According to one existing system developed by Lafarge Canada Inc., a funnel is removably mounted at the end of the truck discharge chute before the hopper and chute are rinsed. The funnel directs rinse water and sediment adhering to the hopper and chute into a 5 gallon bucket which is positioned on the ground. The operator is then required to lift the bucket and carry it to a 15 gallon pressurized tank which is mounted on a truck frame immediately behind the truck cab. The contents of the bucket are then carefully dumped into the tank inlet through a metal screen which filters out larger size aggregate granules. After the tank is pressurized, a discharge valve is opened and the sediment and rinse water is blown through a discharge hose into the truck mixing drum.
The Lafarge system suffers from several shortcomings. The need to manually lift the 5 gallon containment bucket from ground level, carry the bucket to the pressurized tank, and carefully discharge the bucket contents into the pressurized tank inlet mounted at waist level requires considerable manual labour and increases the risk of lower back injuries, especially in older workers.
The valves of the pressurized tank also have a tendency to become clogged with slurry. This increases maintenance costs and results in reduced operator compliance. Further, depending upon the location where the pressurized tank is mounted, it may not be possible to generate a sufficient degree of air pressure in the tank to fully discharge the entire tank contents into the truck mixing drum which exacerbates the clogging problem.
The need has therefore arisen for an improved system for containing concrete truck wash-off and automatically recirculating it back into the mixing drum of the truck.